Conventionally, there have been considered various molding methods for transferring a configuration of the cavity surface of a mold to a resin with high accuracy, thereby improving the external appearance of a molded article on injection molding of the resin within the mold. For example, in the plastic injection molding method (an injection molding method) disclosed in Patent Document 1, the temperature of mold during injection molding is controlled based on the glass transition temperature of a resin where a resin material is non-crystalline, while the temperature of mold is controlled based on the melting point of a resin where a resin material is crystalline.
More specifically, a mold surface (cavity surface) in contact with a molded article is heated at a temperature rising speed of 2 (° C./s) (2° C. per second) or higher to the glass transition temperature of the resin where the resin material is non-crystalline and to a predetermined temperature equal to or higher than the melting point of the resin where the resin material is crystalline. Then, while the temperature of the mold surface is kept at the predetermined temperature, the resin is filled into a cavity of a mold. Further, after the resin has been filled, the mold surface is cooled at a temperature falling speed of 2 (° C./s) or higher.
The mold is controlled for temperature in the manner described above, by which the resin is decreased in temperature to a lesser extent than conventionally when the resin is in contact with the mold, thus improving transfer properties of the resin. Further, since the resin is also decreased in viscosity, the resin surface which is in contact with the mold surface can be easily distorted, thus making it possible to reduce the inner pressure of the resin necessary for the transfer with pressure.